Improvement in tempering and harden ing steel and iron



' filed in the archives of the Patent Office.

UNITED TAT'ES HORACE VAUGHN, or PROVIDENCE, RHODE ISLAND.

IMPROVEMENT IN TEMPER ING AND HARDENING STEEL AND IRON.

Specification forming part of Letters Patent No. 19,804, dated March 30, 1858.

To all whom it may concern:

- Be it known that I, HORACE VAUGHN, of the city and county of Providence, and State of Rhode Island, have invented a new and Improved Method of Hardening and Tempering Steel and Iron; and I do hereby declare that the following is a full and exact description thereof, and for which a caveat of date J anuaary 2,1857, and filed August 5, 1857, has been Patented in England December 29, 1856.

. The nature of my invention consists in heating the articles to be hardened-and tempered in a bath composed of certain chemical agents or in gredlen ts in a state of igneous fusion, from which bath the articles to be hardened and tempered are removed, when sufficiently heated, and dipped into water, oil, or certain solutions in the usual manner.

To enable others skilled in the art to make and use my invention, I will proceed to the necessary description. In performing my invention the chemical agents or in gredientsrequired for m akin ga bath suitable for hardenin g'and tempering articles of steel consist of bichromate of potash, chloride of sodium, and prussiate of potash, mixed togetherin the proportions of two pounds of bich'romate of potash, twelve poundschloride of sodi'iini, and four pounds of prussiate of potash. The quantity of prussiate of potash may be diminished by adding some ground bone or pulverized animal charcoal to the above ingredients. These ingredients, after being pulverized and mixed together, are placed in a box of iron, or into a vessel of any other suitable material and of the required shape, which is put into'a furnace similar to those used for heating crucibles, or for case-hardening or for other purposes 5 or the vessel in' which the bath is made may be heated in any other manner. I prefer to cover the ingredients with pounded wood-charcoal to prevent the escape of the gases during the process of heating 5 or the pounded wood-charcoal, as it possesses hardening qualities, may be mixed vwith the other ingredients. The vessel is heated until the ingredients are in a state of igneous fusion, thereby forming a bath into which the articles to be hardened and tempered are plunged and allowed to remain until they are sufficiently f fusion.

heated. The length of time required for heat:

When the articles have acquired thesame temperature as the bath they are taken from it and dipped into water, oil, or certain'solutions in the usual manner. Other articles are then put into the bath and taken out when heated, the same bath answering for a great number of operations.

In some cases the articles to be hardened and tempered are placed in a suitable vessel and the ingredients above mentioned, or others possessing the same or similar properties, are put into the vessel with the articles. The whole are then placed in the furnace and heated until the ingredients are in a state of igneous fusion. The articles are then removed from the vessel and dipped into water, oil, or

certain solutions in the usual manner, as de-- then placed in a suitable vessel or crucible and heated until they are in-a state of igneous The articles to be hardened are then put in the vessel or crucible, and. the whole may be covered with powdered wood-charcoal to prevent the escape of the gases, to add to the hardness. When the articles have been in the bath a sufficient time to carbonize the iron they are taken out and dipped'into water or any prepared solution, as usual. In pre paring the above bath the quantity of prussiate of potash may be increased or reduced by adding more bone-dust or animal charcoal, and instead of ten per cent of bichromate of potash five per cent. of it, with five per cent. of borax, may be used.

When the articles have been removed from the bath others may be put in, as before de scribed. 1

When articles of cast-iron or malleable castiron are to be hardened I prepare the bath in the manner above described in reference to hardening articles of wrought-iron; but I re- 2 v L504 a ents to form a bath in a state of igneous fusion.

It is sometimes desirable to heat articles to be hardened and tempered before they are plunged into the baths above described. The object of this is to economize time in the operation. This preliminary heating of the articles may be effected by placing them in a furnace or a smiths fire, or otherwise.

In these specifications I have given the prineiples of the invention; but the operator will have to exercisejudgment in their application.

He should avoid particularly the use of wet tongs or other tools which will convey water to the bath.

The above-mentioned ingredients are those which I consider best; but I do not confine myself strictly to the foregoing proportions or m aterials, as others of a similar and cheaper character may be used, but with a less effect.

For hardening steel files and spindles for cotton and woolen machinery and some kinds of edge-tools I make a bath of chloride of sodium alone, or mix saltpeter or any of the potashes with it, or else borax or soda with or without ground bone.

For hardening iron, chloride of sodium with prussiate ofpotash in a state of igneous fusion, with or without the substances heretofore mentioned, will answer to a certain extent.

Cast-iron and steel tools may be hardened by any of the foregoing preparations.

The advantages resulti'n gfrom this improved method of'hardening and tempering are First. The articles to be operated upon, instead of being exposed to the direct influence of the products of combustion while being heated, as in the ordinary mode of operation, are immersed in the bath, and consequently protected from the air. They are therefore uniformly heated in all parts simultaneously and are free from the injuries resulting from unequal heating,.which in the ordinary mode are unavoidable.

Second. The temperature required to maintain the bath in a state of igneous fusion may be varied according to the hardness required. The articles to be operated upon, after remaining in the bath a suificient time to acquire the same temperature, must, when taken from the bath and dipped into the water or oil, or other solutions, become equally hard.

Third. When articles of steel are operated upon the process ofletting down --that is to say, heating a second time to render the steel less brittle-is in most cases dispensed with.

Fourth. The ingredients of which the bath is composed become chemically combined with the articles of steel, castiron, wrought-iron, or malleable cast-iron, and impart a certain degree of toughness to them, which in most cases is very beneficial.

Fifth. When articles of wrought-iron, castiron, or malleable cast-iron are hardened according to this improved method the hardening pentrates deeper than in the usual mode of case-hardening in the same length of time.

And, lastly, a great savingof time is effected, as the vessel containing the bath may be large enough to contain any convenient number of articles, which are taken out of the bath and dipped into the water or oil, or other solution in succession. In hardening polished articles of steel the biehromate of potash may be reduced in quantity or entirely omitted, and carbonate of potash and borax, combined in equal proportions or used separately, may be employed in its stead in order to prevent the said articles from being colored by the process of hardening, the said biehromate of potash having a tendency to injure the color of the articles to be hardened.

Having thus described the nature of my invention and the manner of performing the same, I wish it to bedistinctly understood that in preparing the baths, as described, I do not confine myself to the proportions given, nor to the ingredients named, asthe proportions may be varied according to the particular object for which the bath is intended, and other ingredients possessing the same or similar chemical properties may be employed. I would also remark that I do not confine myself to the use of all the ingredients at the same time, when combined as described, as for some hardening purposes a bath may be prepared of chloride of sodium, in combination with any of the ingredients named, or others possessing the same or similar properties in a state of igneous t'usion; nor do I claim the use of the withinnamed substances when the same are used in a state of aqueous solution; but

What 1 claim is-- The use ofa bath of chloride of sodium, with or without ferrocyanide or biehromate of potash, or either of them, or of other ingredients In presence of 1%. T. Brncnn'r'r, GEO. O. THOMAS. 

